This invention generally relates to slider-operated plastic zippers intended for use in reclosable pouches, bags or other packages. In particular, the invention relates to methods and apparatus for feeding sliders to a slider insertion device.
Reclosable fastener assemblies are useful for sealing thermoplastic pouches or bags. Such fastener assemblies often include a plastic zipper and a slider. Typically, the plastic zippers include a pair of interlockable fastener elements, or profiles, that form a closure. As the slider moves across the profiles, the profiles are opened or closed. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure elements, etc. Reclosable bags having slider-operated zippers are generally more desirable to consumers than bags having zippers without sliders because the slider eliminates the need for the consumer to align the interlockable zipper profiles before causing those profiles to engage.
Conventional slider-operated zipper assemblies typically comprise a plastic zipper having two interlocking profiles and a slider for opening and closing the zipper. In one type of slider-operated zipper assembly, the slider straddles the zipper and has a separating finger at one end that is inserted between the profiles to force them apart as the slider is moved along the zipper in an opening direction. The other end of the slider is sufficiently narrow to force the profiles into engagement and close the zipper when the slider is moved along the zipper in a closing direction. Other types of slider-operated zipper assemblies avoid the use of a separating finger. For example, U.S. Pat. No. 6,047,450 discloses a zipper comprising a pair of mutually interlockable profiled structures, portions of which form a fulcrum about which the profiled structures may be pivoted out of engagement when lower edges of the bases are forced towards each other.
An improvement in sliders is disclosed in U.S. Pat. No. 6,954,970 entitled “Insertion Apparatus for Attaching Sliders onto Zipper Bags and Film”. This slider can be inserted on the zipper so that the zipper is secured in the slider. As a result, during an opening of the reclosable bag the interlocking closure elements of the zipper will not unintentionally re-engage within the slider. For example, a reengagement of the interlocking closure elements could occur when the zipper opening end of the slider is pushed toward a closed zipper park position. Such a re-engagement can occur during operation of the zipper or if the slider is inserted too far from a slider end stop on the zipper. By reducing the possibility of unintentional re-engagement of the interlocking members of the profiles, production of defective bags is reduced. U.S. Pat. No. 6,954,970 discloses a slider insertion apparatus comprising an activator that opens a first portion of a zipper tape, a pusher that inserts the slider onto a second portion of the zipper tape, and a zipper guide that holds a third portion of the zipper tape closed. The zipper guide and the activator with pusher are manufactured to facilitate forward movement of the zipper tape within the slider insertion apparatus; to properly position the profiles of a section of zipper for slider insertion; and to secure an adjacent section of the zipper when the slider is inserted. A loading rack with a supply of sliders may be part of the slider insertion apparatus, with the loading rack being a mechanically attachable device or module.
Systems for transporting sliders to a slider insertion device are disclosed in U.S. Pat. No. 6,666,626 (incorporated by reference herein) entitled “System for Transporting Sliders for Zipper Bags”. That application discloses feeding sliders into a slider insertion device by means of a feeder tube that only accepts correctly oriented sliders having an asymmetric profile, i.e., one leg of the slider is longer than the other leg. Sliders are launched into the feeder tube by a sender apparatus that is controlled by a programmable controller based on feedback received by the controller from various sensors that detect the presence or absence of sliders at particular locations in the slider transport system. The sliders are pneumatically transported in predetermined quantities from a supply of sliders, e.g., a vibratory hopper, to a loading rack.
U.S. Pat. No. 6,666,626 discloses embodiments in which sliders are transported via a flexible feeder tube that connects an exit port of the sending apparatus with an entry port of a loading rack mounted to a slider insertion device or of the slider insertion device itself. In the case where a single feeder tube is used, the length of that tube must be selected as a function of the available layout at a particular plant or facility. The length of feeder tube will need to be at least equal to the distance separating the exit port of the slider sender apparatus and the entry port of the slider insertion apparatus, which in turn will depend on placement of those apparatus. The placement of equipment is a function of the location and configuration of the available space and the presence of obstacles or impediments to the feeder tube being laid in a straight line. These factors will vary from plant to plant, making it necessary to customize the feeder tube length for each installation of slider insertion equipment. In particular, measurements will need to be made at the site of installation before the feeder tube is cut and shipped by the equipment vendor.
Moreover, when the automated slider insertion equipment is moved from one location in a plant to another location in the same plant or to a different plant, a length of feeder tube that was suitable for one layout of the equipment may become unsuitable when that equipment is rearranged at a new site where new specifications must be met. If a shorter feeder tube is needed, then of course the existing feeder tube can be cut, but in the case where re-installation or re-configuration of the slider insertion system mandates a longer feeder tube, the existing short feeder tube may be rendered unusable.
In addition, the labor involved in measuring a site where slider insertion equipment is to be installed, calculating the length of the feeder tube required, and then cutting feeder tubing to the calculated length must increase the cost of the equipment. Further, errors in measurement or prediction could give rise to inefficiencies and economic loss.
There is a need for a feeder tube system that can be easily adapted to suit different manufacturing plant circumstances. In particular, there is a need for a slider feeder tube system in which the overall length of the slider feeder tubing can be varied to fit the requirements of any installation.